Electric regulator for furnaces and other apparatus



Feb'. 6, 1940. L T Re. 21,345

ELECTRIC REGULATOR FOR FURNACES AND OTHER APPARATUS Original Filed July14, 1933 2' Sheets-Sheet 1 Feb. 6,-1940. G. A. F. MACHLET 21,345

ELECTRIC REGULATOR FOR FURNACES AND OTHER APPARATUS O'rigifial FiledJuly 14, 1933 2 Sheets-Sheet 2 k. \W |||||r|||||||.V N t 2Q In venfor:

Attorney.

- Reicmed Feb. 6, 1940 PATENT OFFICE ELECTRIC REGULATOR FOR FURNACES ANDOTHER APPARATUS George A. F. Machlet, Elizabeth, N. J.

Original No. 2,056,285, dated October 6, 1936.

Serial No. 680,494, July 14, 1933..

Application for reissue October 5, 1938, Serial No. 233,498

30 Claims.

whose action only a weak electric current is 10 available. It iscontrived to utilize the delicate actuating member of l a sensitiveinstrument, for

effecting delicate regulation of a working apparatus, such, for example,can furnace or heater, "but without retarding the movement and therebydetracting from the, sensitiveness of the indicating member. The objectin imposing no work upon the automatic controlling device, is to insuredelicacy and precision of its action. Heretofore it has been thepractice to set a point which was reached by an overadvance of thecontrolling device, at which point a reversal was efiected. Anotherpoint was set for limiting the ensuing reverse travel of the controllingdevice. The latter continually vibrated or stepped to and fro betweenthose points. By means of the present improvements, the automaticcontrolling or determining device may move from an idle position to theexact point desired, and there settle and remain motionless orsubstantially so, throughout the operation of the workapparatus, notstepping either up or down therefrom.

The heat of a furnace for example, may be accurately and steadilymaintained at any de sired point. Fluctuation of itsheat may besubstantially eliminated, as the automatic regulator will promptlysettle at the point at which the precise necessary flow of fuel will besupplied to the furnace, without liability to the continual 4ooverheating and under-heating eflects which are commonly due to thefluctuations of standard heat-controllers. 7

Equivalent advantages are obtainable from the invention in many otherinstances where it is desired to effect effortless and delicateregulation; the invention by no means being limited to heat-controllingapparatus.

By employing a condenser-device, this inven tion provides that amoving'member of a measuring instrument, such as the needle ofapyrometer for example, shall produce electrical capac-' ity variationsproportional to the movements of said member. The usual graduated scaleof a pyrometer or other instrument may or may not 55 be present as theadvantage of the automatic control can be realized even though there isno scale used for co-operation with the needle. By the employment of asuitable electric indicating circuit, these capacity variations arecaused by the novel automatic controller to efiect proportionalvariations in consumption or flow of an electric current in a separatenovel controlling circuit, the variations being due to fluctuations inthe condition of the major or work apparatus to which said indicatingcircuit is connected. 10 The current fluctuations in the controllingcircuit may be utilized to govern or control the condition of such majorapparatus, and also to record the fluctuations if desired.

How-these proportional capacity variations are utilized to effectproportional and stepless control and preferably recording of thecondition indicated by the indicating instrument, will be explained inthe following description of a typica application of this controlprinciple.

In the preferred form of the invention, there is utilized as oneelement, 'a conventional variable condenser of the type generallyemployed for tuning a radio-receiver to the desired. frequency, andconsisting of a rotor-set and a stator-set of condenser-plates, whichare mounted in a manner permitting the rotor to be rotated while thestator remains stationary. As the rotor is turned, its plates advanceinto, or recede from, the spaces between the plates of the stator,without, however, effecting contacts with these plates. Since thecapacity of this main condenser is determined partly by the overlappingor eifective' areas of the plates, it can be readily seen that thecapacity of the condenser is determinable 85 solely by the relation ofthe rotor-plates to the stator-plates, since all other capacity-afiecting factors ordinarily remain constant.

With the aforesaid main condenser there is associated, to gain thedesired results, an aux- 40 iliary condenser. The latter is used inconjunction with the pyrometer or other indicator device and the furnaceor any other apparatus or device that it is desired to control; Theauxiliary con- .denser has a statorand a rotor. The rotor, in thepresent illustration, may consist of the indidicating needle of agalvanometer that forms part of a pyrometer-train. The auxiliarycondenser-device may'have comparatively little capacity, and is tunedautomatically. The main condenser may be regulated or tuned manually. Tobe specific, the indicating needle (or itsequival'ent) of a galvanometeror other sensitive indicating instrument, is made to serve as a rotor,being adapted to pass between plates of a furnace.

of an electrode that is constructed in the form of a fork. Theindicating needle, together with the electrode, may actually constitutean aux- ,iliary variable condenser, since the electrode represents theauxiliary stator-plates, while the indicating needle may represent theauxiliary rotor.

It is quite obvious then, that when the indicating needle hovers in theproximity of the electrode, responsive to fluctuations in thepyrometer-circuit, it is automatically varying the capacity of thevariable condenser of which it is a part, in proportion to the extent ofits movement. Since it at no time touches the electrode, the needle isnot obstructed, and it follows that the needle may, if desired, performits usual indicating function. In any case, the needle or coil of theinstrument is not mechanically affected or retarded.

The main condenser, taken together with the auxiliary condenser, forms acontrol-element,

which is subject to fluctuations due to the movements of thegalvanometer-needle in proximity to the auxiliary stator. Thefluctuations of the needle affect the capacityof the auxiliary condenser(the rotor of the main condenser remaining motionless), and the rate ofoscillation of the circuit in which. it is incorporated is increased ordiminished accordingly, thus increasing or diminishing the rate ofconsumption of electric current jointly controlled by the condensers,and automatically causing reduction or increase in the flow of fuel tothe furnace, or corresponding change in other major apparatus.

It will be understood that a thermo-couple is inserted in the furnace,to enable variations in the heat of the furnace to set up fluctuationsin the electric current passing through the temperature-indicatinggalvanometer having a coil, and that the galvanometer is employed incontrolling the heat of the furnace automatically; thegalvanometer-needlebeing connected to means 'for increasing ordiminishing the fuel-supply to the desired point, and then maintaining auniform flow, as may be required, in order to keep the furnace at asteady heat.

The galvanometer-needle (independently of the usual scale) for thispurpose is utilized for performing the function of varying the capacityof the condenser-element of an electric oscillator. Fluctuations in therate of oscillation are caused to modify the rate of flow of fuel to theInstead of a heat-producer, the invention may be used for regulatingother producers,as for example dynamos, and the variations in thecondition of the producer may be utilized for the automatic regulationthereof. It is also available for. regulating non-productive majorapparatus.

Other features and advantages will hereinafter appear. i

In the accompanying drawings,

Figure 1 is a sectional elevational diagram representing a gas-furnacewhose temperature is being regulated by the present invention; theairvalve being open and the furnace warming up to the point set by thestator of the auxiliary condenser; the needle being in motion from idleposition toward said auxiliary stator.

Figure 2 is a part-sectional diagram in side elevation, showing. theposition at which the reg-, :latzr maintains the furnace at apredetermined ea" small stator, the latter consisting of the tinesFigure 3 is a fragmentary plan of the tips of the needle and theco-operative stator.

Figure 4 illustrates the connections of the v stator and rotor of themain condenser.

Figure 5 is a plan of the condenser seen at Figure 4.

Figure 6 shows a modified form of automatic condenser-elements.

Figure 7 shows a-needle made of material not serviceable for the plateof a rotor; the stator matically regulated, includes a solenoid l I,whose core l2 may pull down a spring-lifted valve-rod l3, havingbalanced valves l4, [5, to close ports l6, I1 in a chest I8, which issupplied with air through a pipe l9, and which delivers a delicatelyregulated .flow of air through outlets 20, 2!, to a conduit 22 runningthrough a fuel-injector (not shown) to a furnace 23; the injector havingthe' usual provision for mixing compressed air with the fuel-gas. Thefurnace and the solenoid are here used for the purpose of illustration,as the invention is applicable to regulating an electric current for avariety of purposes.

Although power could be obtained from batteries, it is preferred toutilize current supplied by the local electric-light line, through plug24. However, since this is generally an alternating GO-cycle current of110 volts, it is first necessary .to transform it to the proper voltagefor a filament-supply. It is further necessary to convert it into directcurrent of proper voltage for the plate-supply of a vacuum tube. This isaccomplished by connecting plug 24 to the primary coil 25 of a3-secondary transformer, having a grounded core 21, ina circuitdiagrammatically enclosed in the dotted area A. A current of highervoltage is obtained in secondary coil 23. A rectifier-tube 28 containsopposite plates 29,

30 in circuit with the grounded secondary coil n 26. The filament 3| ofthe rectifier-tube is in-' grounded core 40. Circuit 31 may also includea milliammeter ll, and a grounded voltmeter 42, for making sure that thevoltage is right.

r The current flowing through plate-circuit 31 passes through thesolenoid H, and pulls down the core I! against the tension of supportingspring 45. The return leg 31' of the circuit, leading from the solenoid,is connected to the middle of secondary coil 32, the positive terminalof the power-supply.

Y 'lhe balanced solenoid-operated valve H determines the amount of fueldelivered to the furnace. The air-valve I3, and its valve-plates I4, I5,together with the solenoid-core l2, co-operate with spring 45, so thatthe valve is kept in its maximum open position while the minimum amountof current is passing through the solenoid, as shown in Figure 1. As theflow of current through the solenoid gradually increases, the pull onthe plunger l2, counteracting the spring tension, will correspondinglyincrease, thereby effecting a gradual closing of the valve. The quantityof fuel supplied to the furnace is in inverse proportion to the amountof current passing through the solenoid.

Since the solenoid is shown connected in series with the plate-powersupply 31 of the vacuum tube 35, it is evident that the amount ofcurrent flowing through the solenoid depends entirely upon the amountconsumed by vacuum tube 35.

In the grid-circuit 38 of the oscillator is a condenser 50, and a manualtuning coil is shunted around a grounded variable condenser at 52. Byadjustment of 52, the capacity of the condenser may be raised orlowered, and the frequency of oscillations proportionally decreased orincreased. Increase in rate of oscillation involves increasedconsumption of electric current, and more current therefore passesthrough the solenoid H, pulling down the core [2 and valve 13 in closingdirection. Thus the heat of the furnace 23 may be reduced at will. Itwill be perceived that by an adjustment of the capacity of 52 in theoppositedirection, the frequency of oscillation will be decreased, lesscurrent will be consumed, the pull of solenoid II will weaken, and thespring 45 will raise the core and valve 13, to admit more air to bemixed with fuel and supplied to the furnace 23. The heat of the furnaceis thus manually settable or controllable.

To enable the furnace to vary its own fuelsupply, and thereby regulateits own production of heat, there is provided a pyrometer-circuit 53, inwhich a weak current of electricity is generated by the heat of thefurnace, by means of an element 54. Included in this circuit is agalvanometer 55, by means of which the strength of the current and hencethe heat of the furnace may be ascertained. The tip of thegalvanometerneedle 56 is bent over at 51, and preferably overlies abowed scale 58, indicating the furnace temperature.

As an additional function, the galvanometerneedle 56 is utilized as arotor, to co-operate with a stator, to automatically tune or effectvariations in the general condenser capacity, and consequently automaticvariations in the. frequency of oscillation in the circuit of grid 31.For this purpose, there is associated with the condenser 52 an auxiliarycondenser or tuning device, which is connected in parallel with 52 by acircuit 59, which includes the rotor or galvanometer-needle 56, and isgrounded at 60. The main condenser 52 is grounded at 6|.

The use of a scale is not necessary in all cases. The coil of thepyrometer will effect the tuning movement of needle 56, whether thescale is present or absent.

The groundings shown in the drawings are negative.

The stator-member of the auxiliary condenser is shown in the form of aradial arm 62, connected to 59 and 52, and having its tip bent over andforked at 63, so that the tongue-portion 51 of the galvanometer-needle(or auxiliary rotor) 56 can pass between the tines of the fork. The

fork-tines act as stationary plates, and constitute the stator,auxiliary to the stator at 52, while the bent-over tongue or point 51 ofthe needle acts as an adjusting plate relatively to 63,

and by its automatic movement produces a tuning or variation in thecapacity .of the auxiliary condenser 51, 63, and hence eifectsalteration of the frequency of the oscillations in the grid-circuit 31,with consequent alterations in the volume of current passing through thesolenoid ll, thus altering the position of the air-valve I3, to vary thesupply of fuel to the furnace.

The novel automatically adjustable statorarm or electrode 62 isconstructed in the form of a fork, whose tines are spaced sufficientlyto allow ample clearance for the needle or rotor 56 or 51 to passbetween them. The width. of these tines (Figure 3) may be equal to thewidth of the indicating needle.

Notwithstanding its added function as a rotor, the normal movement ofthe novel heat-indicating needle is not impeded, and the galvanorneter55 will preferably perform its usual function, as though the describedadditional service had not been required.

Outside of the galvanometer-casing 55, the radial rotor-arm 62 may beconnected to an adjusting arm 64-, having a handle.65, whereby arm 62may be set for any point of heat which the furnace is desired to reachand maintain. This adjustment of 62 may be attended to after thecapacity of the tuning condenser has been approximately adjusted at 52.The furnace-heat will either build up or decline to the point at which62 is set, and will there remain.

The auxiliary stator-arm 62 is so mounted concentrically with thegalvanometer-needle 56 that the arm may be adjusted to any desired pointin the are described by said needle.

The indicating needle 56, together with the stator or electrode 62, maythus be regarded as constituting a small variable condenser-element, thecapacity of which varies in correspondence with the change in positionof the needle relatively to the electrode. The maximum capacity isattained when the entire width of the indicating needle lies within thetines of the electrode; the minimum, when the needle has receded nearlyout of effective range with the electrode. Very little capacity changeis realized, until the leading edge of the indicating needle enters thespace determined by the tines of the electrode. From this point on, thecapacity increase is very rapid, and reaches maximum when the entirewidth of the indicating needle is between the tines of the electrode.This narrow or restricted zone, in which the ratio of capacity change toindicator movement is very high, is an important controlling zone.

Since the electrode 62 is pivoted at 66 concentrically with needle 56and galvanometer-coil 61,

it results that 62 may be moved to any position in the are described bythe needle, and it is thus evident that the position of the controllingzone may be varied, and that any desired temperature or other conditionof the apparatus may be reached automatically and there maintained.

The current consumption depends upon the frequency to which theapparatus is tuned. Tuning is accomplished by means of variablecondenser 52, together with the small auxiliary variable condenserformed by the co-operation of the indicating needle and the electrode.The condensers are connected in parallel across the gridcoil- 5|.

a fall in temperature).

When the circuit is in operation, more or less current will be consumedby the vacuum tube 35,

depending upon the adjustment of the auxiliary stator 62, 63 and theposition of the rotor or indicating needle 56, 51. This change incurrent consumption may be indicated by milliammeter 4| connected inseries with the vacuum tube plate supply line 31.

After the furnace has been started in the usual manner, the power forthe control circuit, which 'is diagrammatically indicated at theboundary line-B, is switched on at 24, the electrode 62 is adjusted forthe desired temperature (say 1650 degrees F.), and the variable atcondenser 52 is tuned for a value just below that at which themilliammeter 41 indicates an increase in current consumption,

If it is assumed that the control range extends over degrees, thefuel-control. valve I3 will remain in its maximum open position untilthe indicating needle 56 of the galvanometer 55 indicates a temperatureof 1645 degrees. If the indicating needle advances beyond this tempera:ture, it effects an increase in capacity in the condenser 56, 62. Thiscauses an increase in the plate-current consumption of the vacuum tube35. Since the solenoid ll of the control-valve I3 is connected in serieswith the plate-supply 31 of the vacuum tube 35, it is apparent that thepull on its core l2 will also increase, thereby efiecting a gradualclosing movement of the fuel-control valve= l3. V

When the temperature has reached 1655 degrees, the control-valve 13 willhave assumed its minimum desired position, and, since, at this positionthe furnace is supplied with a scarcity of fuel, the temperature mustdrop. As the temperature falls, the described operation reverses, thecontrol-valve gradually reopens, and the fuel-supply increases, therebychecking the temperature drop.

It is evident then that after a short time, the fluctuations of theindicating needle will cease, and it will settle in a position that willcause the control-valve continually to admit a quantity of fuel in thefurnace that will just offset the latters heat losses, therebymaintaining the temperature constant This position of the indicatingneedle must therefore lie between 1645 and 1655 degrees (since at 1645the control-valve is in its maximum position, thereby causing a rise intemperature, and at 1655 is in its minimum position, eflecting Theindicating needle will come to rest at 1650 degrees, which is thedesired temperature in this illustration, and there remain.

In practice, even if there is some slight vibration of the needle at thestart, still it promptly settles at the desired point, and remainsmotione less.

In instances where the indicating needle may not be a conductor ofelectricity, the device shown at Figure 7 is'used. In this case, thetines of the adjustable electrode! are insulated from one another,thereby constitutin a small fixed aux,- iliary condenser in themselves.needle 56 in passing between them, carries the capacity by changing thedielectric medium of the auxiliary condenser, as will be understood.

Figures 8 and 9 show how capacity variations can be caused by a'movingliquid 68. The indieatingfunction performed by the liquid may be thesame as that performed by the moving indicator in thepreviously-explained cases. change is in the form of the electrode orelectrodes employed. The liquid moves in an in- The indicating Theclined adjustable glass tube 69. The stator is in the form of a collarI0. Tipping of the tube causes the mercury to flow into the collar, toincrease the capacity as explained.

The invention is not limited to the described means for transforming thecapacity variations produced by the movement of an indicator of anindicating instrument, into proportionate variations of electricalenergy.

It will be understood that power may be derived from a battery ifdesired, instead of from an electric-light line, since the positive poleof the battery would be at 32 and the negative at 26.

Many other variations may be made within the scope of the invention, asfor example the indicating needle may have tines, and the auxiliarystator may be in the form of a tongue to be forked by the tines.Portions of the improvements may be used without others.

I claim:

1. The combination with a furnace having a regulator, and meansresponsive to said regulator to control the supply of fuel to thefurnace, of control means for keeping the furnace constantly andsteplessly at a desired temperature with practically no temperaturedrift; said control means comprising a temperature-measuring circuitincluding a galvanometer having a needle movable in accordance withvariations in the furnace temperature, an electrical circuit separatefrom said temperature-measuring circuit and including a circuit elementadjustable to vary the current flow in said electrical circuit inproportion to variations in the furnace temperature, said circuitelement comprising a relatively fixed member and a member carried by andmovable with the galvanometer needle, and electrically operating meansresponsive to such variations in current flow for producingcorrespondingly proportional operations of said regulator.

2. The combination of a major apparatus, a delicate regulator therefor,an indicating instrument in an independent minor electrical circuit andhaving a member displaceable in accordance with variations in a functionof said major apparatus measurable by said instrument, a mainoscillatory electrical circuit, means including said instrument memberfor varying the capacitive reactance and thereby the output power ofsaid main circuit in proportion to displacements of said member, andmeans responsive to the variations in output power for producingcorrespondinly proportional variations in the adjustment of saidregulator.

3. The combination ofa tube circuit; a galvanometer; means for enablingthe change in position of the needle of the galvanometer to bring aboutfrequency variation in the tube circuit; a stator co-operating with saidneedle to form a small variable condenser, the needle being unobstructedby the stator, and so free to assume any position on the galvanometerscale; said condenser being shunted across a, grid coil which isinductively related to an anode coil, so that as the indicating needlehovers in the proximity of the stator an inductive relation between thetwo coils is affected, a change in the anode current of the tube beingeffected; means including a solenoid in series with the anode supply fortransforming the current variations into equivalent mechanicalvariations; and means to utilized these mechanical energy variations tocontrol a major apparatus.

4. In combination, an oscillatory electric cirminutest change infrequency automatically causes a proportional and relatively greatchange in current flow, a controlling mechanism and means actuated byand in proportion to such changes to adjust said controlling mechanismto bring about automatically required variations -in a control power.

5. In combination, a major apparatus, an indicating instrument having amovable indicator normally stationary during the operation of saidapparatus, but movable in response to changes in the condition of theapparatus, an electric circuit whose capacity is varied by movements ofsaid indicator, whereby the flow of current in said circuit is varied,apparatus-regulating means responsive to the variations in the flow of"current, said movable indicator freely hovering in proximity to anelectrically charged element connected in either the grid or platecircuit of an electronic tube, thus causing variations in the amount ofcurrent flowing in the tube circuit, and an electro-magnetic regulatingdevice inserted in the tube supply circuit and operated by the currentin the tube circuit.

'6. The combination with a major apparatus having a characteristic thatmay vary in magcuit in response to and as a continuously vari-.

able function of the needle displacement, said reactance meanscomprising a movable element carried by said needle and a relativelyfixed stator element, means supporting said stator element foradjustment to determine the zone of operation of said movable elementand stator element, and means for translating the changes in currentflow in the oscillatory circuit into,

proportional mechanical displacements.

7. The combination with a major apparatus, and means including aresonant circuit for controlling said apparatus in response to and inpro-- portion to variations in the flow of oscillatory current in saidresonant circuit; of an electrical measuring circuit including avoltmeter having a needle displaceable in accordance with progressivechanges in a condition of said major apparatus; reactance-adjustingmeans including said needle and a stator element for transforming theneedle displacements into proportionate changes in the magnitude of theoscillatory current flow in said resonant circuit, andmanuallyadjustable means for determining the operating zone of saidreactance-adjusting means;

8. In combinatiom'an oscillator, a major apparatus to be controlledthereby, means for manually tuning said oscillator, auxiliary means fortuning said oscillator within a limited range determined by theadjustment of said manual tuning means, measuring means controlled by avariable condition of said major apparatus for actuating said auxiliarytuning means in proportion to the magnitude of that condition,continuously adjustable means for controlling said major apparatus tomaintain the condition thereof substantially constant, and meansoperable in response to the actuation oi said auxiliary tuning means forproducing proportionate changes in said continuously adjustable controlmeans.

9. The combination of a major apparatus, measuring means responsive todelicate changes in a condition of said apparatus, and electrical meansfor regulating the operation of said major apparatus in proportion tothe tendency of the measured condition thereof to depart from apreselected standard; said regulating means comprising an oscillatorycircuit, means including said measuring means for varying an electricalcharacteristic of said oscillatory circuit progres-v sively inproportion to the measured variations in the condition of the apparatus,adjustable means for controlling the operation of the major apparatus toinfluence the measured condition thereof, and means responsive to saidproportionate changes in electrical characteristic of said oscillatorycircuit for producing correspondingly proportionate adjustments of saidcontrol means.

10. In combination, a major apparatus having a condition subject tochange during operation of the apparatus, means for affecting the saidcondition and including a regulating device to be adjusted in accordancewith changes in the condition of the apparatus, a measuring systemresponsive to changes in the condition, and an electrical networkseparate from said measuring system for adjusting said auxiliary devicein response to the measured changes in the condition of the apparatus;said network including an oscillatory circuit and a second circuit,means for establishing an oscillatory current fiow in saidoscillatory-circuit and a direct current flow in said second circuit,adjustable reactance means including the measuring system for varying anelectrical characteristic of said oscillatory circuit progressively inproportion to changes in the measured condition, coupling means betweensaid circuits operative to vary an electrical characteristic of saidsecond circuit progressively in accordance with-changes in theelectrical characteristic of the oscillatory circuit, and means in saidsecond circuit for adjusting said regulating device progressively and inproportion to changes in an electrical characteristic of said secondcircuit.

11. In combination, a major apparatus having a condition subject tochange during operation of the apparatus, a control device to beadjusted in accordance with changes in the condition of the apparatus, ameasuring system responsive to changes in the condition, and anelectrical net- 'work separate from said measuring system for adjustingsaid control device in response to the in proportion to changes in themeasured condition, coupling means between said circuits operative tovary the flow of direct current in said second circuit progressively inaccordance with changes'in the electrical characteristic of theoscillatory circuit, and means controlled by current flow in said secondcircuit for adjusting said control device progressively and inproportion to changes in an electrical characteristic of said secondcircuit.

12. The combination with a main source of electric. current, anoscillator including a vacuum tube and a resonant circuit determiningthe frequency of the generated oscillatory current, an electricallyoperable adjustable regulator, a major apparatus dominated by saidregulator, means responsive to changes in condition of said majorapparatusfor proportionately varying an electrical characteristic ofsaid oscillator; and means responsive to changes in said electricalcharacteristic for adjusting. said regulator progressively in proportionto the electrical characteristic changes.

'13. The combination of a main source of electric current, an oscillatorhaving a filament connected to said source of current, an electricallyoperable regulator in circuit with the plate of said oscillator and withsaid source of current, a tuning condenser device having a connectionwith said grid, a major apparatus subject to change of conditions, andmeans dependent upon the condition of the major apparatus for operatingsaid tuning device to vary the condenser capacity and the rate ofoscillation and thereby control the consumption of current in the platecircuit to cause said electrically operable regulator to eifectcorresponding regulation of said major apparatus.

14. The combination of a main source of electric current, an oscillatorhaving a filament, plate and grid, said filament being connected to saidsource of current, an electrically operable regulator in circuit withsaid plate and said source of current, main and auxiliary condensersjointly in circuit with said grid, said auxiliary condenser including acapacity-altering member, a major apparatus, subject to change ofcondition, and means dependent upon the condition of the major apparatusfor moving said capacity-altering member toward or from the stator partof said auxiliary condenser, whereby variations due to change ofcondition of the major apparatus are produced in the joint capacity ofthe condensers and consequently in the rate of oscillation, andconsumption of current is thereby controlled in the plate circuit, andsaid electrically operable regulator is consequently caused to effectcorresponding regulation of said major apparatus.

15.The combination of a furnace, a main source of electric current, anoscillator having a filament connected to said source of current, andalso having a plate and a grid, said plate in circuit with a solenoidand also with said source of current, main and auxiliary condensers incircuit with said grid, said auxiliary condenser including a rotor orequivalent operable by a voltmeter coil to an extent dependent upon theheat of the furnace, whereby variations due to heat are produced in thejoint capacity of the condensers and consequently in the rate ofoscillation, and consumption of current in the platesolenoid circuit-iscontrolled, and means to enable the solenoid to regulate the supply offuel to the furnace.-

16. The combination with a furnace, of an electric circuit affected bythe heat of the furnace and including a voltmeter coil, a transformerfor connection to an electric line and having primary and secondarycoils, including one secondary coil for lowvoltage, and also including asecond secondary coil in circuit with a rectifier, and also including athird secondary coil in circuit with the filament of anoscillator havingplate and grid, said plate in circuit with a solenoid and the first ofsaid secondary circuits, means for enabling the solenoid to regulate thesupply of fuel to the furnace, a main variable condenser in circuit withsaid grid, and an auto matic auxiliary condenser including an auxiliaryrotor or equivalent operated by said voltmeter coil, whereby variationsin the capacity of the auxiliary condenser are produced by fluctuationsin the heat of the furnace operating through the voltmeter-coil current,the frequency of oscillations in said main and auxiliary condensers be-1 ing dependent upon the automatic alterations in the capacity of thecombined main and auxiliary condensers, whereby the consumption ofcurrent in the plate-solenoid circuit is controlled and the supplyoffuel to the furnace regulated.

1'7. The combination with a furnace, of means for supplying fuel to thefurnace, a pyrometer for the furnace including an electric circuit, agalvanometer being included in said circuit and I having a needle, meansfor supplying an alternating current of electricity, a transformerhaving primary and secondary coils for transform ing the alternatingcurrent into a current of low voltage, said transformer also having asecond secondary coil in circuit with a rectifier tube, said transformeralso including a third secondary coil in circuit with a low voltage.filament-heating circuit in an oscillator tube, said tube having a plateand grid, the'plate being included in a circuit having a solenoidprovided with a core,

means operable by the solenoid for regulating the supply of fuel to saidfurnace, said plate and solenoid circuit being connected to the first ofSaid secondary coils, the grid of said oscillator being included in' acircuit with the stator of a variable condenser for increasing ordecreasing the frequency of said oscillator, and an automatic auxiliarycondenser stator to co-operate with said pyrometer needle, the needleserving as the rotor of the auxiliary condenser, said auxiliarycondenser being in parallel with said main condenser, the movement ofthe needle being produced automatically by the heat of the furnace andeffecting variations in the frequency of oscillations in the gridcircuit, with consequent fluctuations in the volume of current flowingthrough the solenoid, to automatically vary the position of thefuel-valve and regulate the supply stator constituting a variablecondenser, the ca- Dacity. of which varies-in correspondence with thechange in position of the needle relatively to the stator, the maximumcapacity of the condenser being attained when the entire width of theneedle lies between the tines of the stator,

and little capacity change being realized until the leading edge of theneedle enters the space between the tines, the zone of needle movementbetween the tines being a controlling zone, said stator being adjustableto any position in the arc of the needle. whereby the furnacecontrolling zone may be set to maintain any desired temperature of thefurnace, a variable condenser cooperating with the aforesaid auxiliarycondenser, said condensers being connected across the grid coil of anoscillator, whereby more or less current is consumed by the oscillatordepending upon the adjustment of the stator and the position of theneedle, and a source of power for said oscillator.

19. The combination with a furnace, of means for securing stepless andproportional control thereof, including a thermo-couple, a galvanometerin circuit therewith and having a grounded needle, an electrodeconstructed in the form of a fork whose tines are spaced sufliciently toallow clearance for the galvanometer needle to pass freely between them,the normal movement of the needle being in no way impeded, the width ofa fork tine being equal to the-width of the needle, the needle togetherwith the electrode or stator constituting a variable condenser, thecapacity of which varies in correspondence with the change in theposition of the needle relativelyto the stator, the maximum capacity ofthe condenser being attained when the entire width of the needle j liesbetween the tines of the stator, and little capacity change beingrealized until the leading edge of the needle enters the space betweenthe tines, the zone of needle movement between the tines being acontrolling zone, said stator being adjustable to any position in thearc of the needle, whereby the furnace controlling zone may be set tomaintain any desired temperatureof the furnace, a variable condensercooperating with the aforesaid auxiliary condenser, said condensersbeing connected across the grid coil of an oscillator, whereby more orless current is consumed'by the oscillator depending upon the adjustmentof the stator and the position of the needle, and a source of power forsaid oscillator, said source of power including a transformer and arectifying tube; and a solenoid-controlled valve for controlling theamount of fuel delivered to the furnace; decrease in current capacitycausing the flow of current to be augmented through the solenoid toeffect a closing movement of the valve, said solenoid being connectedin'series with the plate power supply of the vacuum tube, so that theamount-of current flowing through the solenoid depends upon the amountconsumed by the vacuum tube; the fuel-control valve of the furnaceremaining in its open position until the alvanometer needle advances tothe point of cooperation with the adjustable stator and effects anincrease in capacity in the oscillator circuit.

-thereby causing an increase in the plate curchanges in. an electricalcharacteristic of said oscillatory circuit, and a circuit networkcoupled to and controlled by said oscillatory circuit, said networkincluding electric motor means for transforming said minute changes intoprogres-' sive adjustments of said auxiliary device.

21. The combination with a furnace and a galvanometer having a groundedneedle, an electrode settable'along the path of the needle, the nor.-malmovement of the needle being in no way impeded, the needle togetherwith the electrode or stator constituting a variable condenser, the

capacity of which varies in correspondence with the change in theposition of the needle in proximity to the stator, said stator beingadjustable to any position in the arc of the needle, a manually variablecondenser cooperating with said condenser, said condensers connected inparallel across the grid coil of an. oscillator, a source of power forsaid oscillataor including a transformer and a rectifying tube; and asolenoidcontrolled valve for determining the amount of fuel delivered tothe furnace, and decrease in current capacity causing the flow ofcurrent to be augmented through the solenoid to effect a clos ingmovement of the valve, said solenoid being connected in series with theplate power supply 'of the vacuum tube.

22. The combination with a major apparatus, of an electric circuitaffected by the condition of the apparatus and including a voltmetercoil, a transformer for connection to an electric line and havingprimary and secondary coils, including one secondary coil for lowvoltage, and also including a second secondary coil in circuit with arectifier, and also including a third secondary coil in circuit with thefilament of an oscillator having plate and grid, said plate in circuitwith a-s'olenoid and the first of said secondary circuits, means forenabling the solenoid to regulate the condition of the major apparatus,a main vari-' able condenser in circuit with said grid, and an automaticauxiliary condenser including an auxiliary rotor or equivalent operatedby said voltmeter coil, whereby variations in the capacity of theauxiliary condenser are produced by fluctuations in the condition of themajorapparatus operating through the voltmetercoil current, thefrequency of oscillations in said main and auxiliary condensers beingdependent upon the automatic alterations in the capacity of the combinedmain and auxiliary condensers, whereby the consumption of 'current inthe plate-solenoid circuit is controlled and the major apparatus isregulated.

23. The combination with a major apparatus,

of means for regulating the major apparatus, a

condition-indicating device for the major apparatus including anelectric circuit, a galvanorneter being included in said circuit andhaving a needle,

- means for supplying an alternating current of electricity, atransformer having primary and secondary coils for transforming thealternating current into a current of low voltage,'said transformer alsohaving a second secondary coil in circuit with a rectifier tube, saidtransformer also including a third secondary coil in circuit with alowlvoltage filament-heating circuit in an oscillator tube, said tubehaving a plate and grid, the plate being included in a circuit having asolenoid provided with'a core, meansoperable by the solenoid forregulating said major appara tus, said plate and solenoid circuit beingconnected to the first of said secondary coils, the

grid of said oscillator'being included in a circuit with the stator of avariable condenser for increasing or decreasing the frequency of saidoscillator, and an automatic auxiliary condenser stator to cooperatewith said needle, the needle serving as the rotor of the auxiliarycondenser, said auxiliary condenser being in parallel with controlthereof, including a galvanometer having a grounded needle, an electrodeconstructed in the form of a fork whose tines are spaced sufficiently toallow clearance for the galvanometer needle to pass freely between them,the normal movement of the needle being in no way impeded, the needletogether with the electrode or stator constituting a variable condenser,the capacity of which varies in correspondence with the change in theposition of the needle relatively to 'the stator, little capacity changebeing realized until the leading edge of the needle enters the spacebetween the tines, the zone of needle movement between the tines being acontrolling zone, said stator being adjustable to any position in thearc of the needle, a variable condenser cooperating with the aforesaidauxiliary condenser, said condenser being connected across the grid coilof an oscillator, whereby more or less current is consumed by theoscillator depending upon the adjustment of the stator and the positionof the needle, and a source of power for said oscillator.

25. The combination with a major apparatus, of means for securingstepless and proportional control thereof, including a galvanometerhaving a grounded needle, an electrode constructed in the form oia forkwhose tines are spaced sufficiently to allow clearance for thegalvanometer needle to pass freely between them, the normal movement ofthe needle being in no way impeded, the needle together with theelectrode or stator constituting a variable condenser, the zone ofneedle movement between the tines being a controlling zone, said statorbeing adjustable to any position in the arc of the needle, wherebythecontrolling zone may be set to maintain any desired condition of themajor apparatus, a variable condenser cooperating with the aforesaidauxiliary condenser, said condensers being connected across the gridcoil of an oscillator,

whereby more or less current is consumed by the oscillator dependingupon the adjustment of the stator and the position of the needle, asource of power for said oscillator, said source of power including atransformer and a rectifying tube; and a solenoid for controlling themajor apparatus; decrease in current capacity causing the flow ofcurrent to be augmented through the solenoid, said solenoid beingconnected in series with the plate power supply of the vacuum tube, sothat the amount of current flowing through the solenoid depends upon theamount consumed by the vacuum tube; the control means remaining in itsfully effective position until the galvanometer needle advances to thepoint of cooperation with the adjustable 'stator and effects an increasein capacity in the oscillator circuit, thereby causing an increase inthe plate current consumption of the vacuum tube of said oscillator,said solenoid being connected in series with the plate supply of saidvacuum tube, whereby the control means is gradually brought to lesseffective position.

'26. The combination with a major apparatus and a galvanometer having agrounded needle, an electrode settable along the path of the needle, thenormal movement of the needle being in no way impeded, the needletogether with the electrode or stator constituting a variable condenser,the capacity of which varies in correspondence with the change in. theposition of the needle in proximity to the stator, said stator beingadjustable to any position in the arc of the needle, a manually variablecondenser cooperating with said condenser, said condensers connected inparallel across the grid coil of an oscillator, a source of power forsaid oscillator including a transformer and a rectifying tube; and asolenoid-controlled means for regulating the major apparatus; decreasein current capacity causing the flow of current to be augmented throughthe solenoid to effect reduced eificiencyoi the major apparatus, saidsolenoid being connected in series with the plate power' supply of thevacuum tube.

27. The combination with a furnace and a regulator therefor, of meansfor actuating said regulator to maintain the furnace at a desiredtemperature with practically no temperature drift:

said means comprising an oscillatory circuit, a

control circuit including means for progressively adjusting saidregulator in accordance with changes in an electrical characteristic ofsaid control circuit, means coupling said circuits to correcting errorsascertained in a condition of a primary apparatus by a sensitiveinstrument, without diminishing the sensitivity of the instrument; saidmechanism comprising a control circuit including regulatingmeansadjustable toimpose a progressively varying correctional controlupon the primary apparatus, an oscillatory circuit coupled to saidcontrol circuit to produce adjustments of said regulating meansproportional to changes in an electrical characteristic of theoscillatory circuit, and means including said sensi tive instrument forvarying the electrical characteristic of the oscillatory circuitprogressively in proportion to the error as ascertained by the sensitiveinstrument in the condition of the primary apparatus. a

29. The combination with a major apparatus subject to change incondition thereof during operation, a measuring system responsive tovariations of the condition from a preselected value, control meanscontinuously adjustable to impose a proportionately adjustableregulation-upon an operating factor which affects the condition of themajor apparatus, and an electrical network,

for transforming indications of said measuring system element intoproportionate adjustments of said control means; said network includingan oscillatory circuit coupled to a control circuit; means responsive tosaid measuring system for varying an electrical characteristic of saidoscillatory circuit as a continuously variable function of the changingmagnitude of the measured con dition, thereby effecting a correspondingproportionate variation in a condition of said control circuit, andmotor means operating in response to changes in the condition of saidcontrol circuit to proportionately adjust said control means.

measured by said instrument, and controlled means in saidcontrol circuitactuated in proportion to the progressive changes in the electricalcharacteristic of the oscillatory circuit.

GEORGE A. F. MACHLET.

